This invention relates to a fastener to securely fasten joints, preferably in pressure vessels, pipes, and other structures, intended to isolate internal volumes from the external environment, or in structural joints. The invention may be used to secure a pressure seal in vessel applications, join structural units or tubular members having internal passages. The invention may be used in any application currently utilizing standard bolted flanges or to aid in sealing vessels, pipes, or other structural joints.
In an embodiment of the invention, the fastener is used in a clamp-type connector that can join flange members together in an abutting engagement, creating a pressure seal in order to isolate the joint""s internal environment from its external environment. This embodiment is unique in its controlled contact with the flange members wherein uniform seal integrity is secured and contact surface wear is dispelled.
An embodiment of the invention is especially useful in Delayed Cokers, wherein extremely high temperature and relatively low pressures are generated. It effectively handles the deleterious effects of coke exposure or other xe2x80x9cdirtyxe2x80x9d operations. This embodiment is especially useful in quickly and simply retrofitting existing Delayed Cokers. It can be adapted to the existing flange member disposed on Delayed Cokers without having to use a spool-piece adapter.
An embodiment of the invention is also especially adapted to quickly flange up and safely secure extreme pressure vessels while supplying uniform seal integrity under extreme pressure and to quickly open such secured vessels. Therefore, the invention is advantageous in making high-pressure batch-type operations highly efficient and cost effective. A typical application is high-pressure food processing wherein, under extremely high-pressure, pathogens rupture, leaving food less perishable.
The limitations of the prior art compromised safety to provide quick acting joint connecting devices. The prior art discloses single point failure mechanisms, wherein the failure of only one fastener element can catastrophically rend the joint. There is a need in industry to be able to remote open and close a joint with advantages of a safely articulated fastening mechanism and to do so while providing uniform seal integrity. The prior art is laden with quick acting joint connecting devices that fail to provide significant safety. Failure of these mechanisms prompted the American Society of Mechanical Engineers (ASME) to develop rules in their Boiler and Pressure Vessel Codes that give specific rules for adding safety to xe2x80x9cQuick Actingxe2x80x9d devices. Single acting fastening mechanisms and single point failure devices need secondary back-up retaining elements that assure joint integrity upon failure of the single acting fastening means or single point failure devices. Such retaining elements complicate automated operation, however.
In some installations, pressure vessels, pipes, and structural joints are opened and closed manually under conditions that are hazardous to the people performing the operation. Most prior installations utilize joint connectors comprised of bolted flanges that demand significant manual activity. The basic closing nature of bolted flanges is illustrated in the American Society of Mechanical Engineers"" (ASME) Publication B16.5. Other manually operated prior art for connecting joints comprise threaded, clamped, and breach-lock mechanisms. These labor-intensive designs are not well suited in hazardous environments, however.
Most coke drums have manually-bolted joint connectors to join vessel closures and other structural units to the coke drum, thus closing and sealing the internal environment of coke drum. Coke drums may also have manually bolted connections connecting upstream and downstream pipes to the coke drum. Historically, manually operating these connections to dispose them open or closed has proven to be harmful to workmen and inefficient to production.
Although the prior art provides attempts at simplicity, it does not provide sufficient safety. In analyzing paths of failure, the prior art contains unsafe, single component failure paths that cause the catastrophic opening of the connected joint upon failure. A need exists to create a safe connection by incorporating safe articulation in the fasteners and eliminate all single point failure locations in a connector""s articulation.
The inclusion of safe articulation in a remote operable connector entails additional expense and difficulty. Those skilled in the art can appreciate the benefit of a simple, remote operable fastener that can provide safely articulated connections. The system should be manually operable as well as provide for alternative operation in the event of an interruption of the remote operation. In short, when compared to other remote operable connectors, a need exists for a simpler connection.
This simplicity directly relates to lower operating and maintenance costs and shortened down time for maintenance. In some processes, one day of down time can result in an economic loss far surpassing the initial cost of the remote operable connector. Simplicity in design is highly valued by end users of this technology. The prior art discloses remote operable joint connectors providing multiple fasteners by incorporating overly complex mechanisms. In the process of providing multiple fasteners, the prior art sacrifices simplicity, reliability, and economy.
U.S. Pat. Nos. 5,336,375; 4,820,384; 5,221,019; 5,294,157; 5,228,825; 5,048,876, 5,471,739 and 4,726,76 are clamp-type mechanisms designed to remote assist or perform connecting and disconnecting of joints in pressure vessels. Those skilled in the art recognize that these devices have many limitations and are inherently unreliable, and expensive to manufacture.
Pressure and temperature of the working fluid, mechanical loads, and mechanical properties of the sealing gaskets dictate the magnitude of the gasket crushing clamping force. Gaskets that are suitable for moderate to high temperatures and pressures are not generally self-energized elastomers. A self-energized gasket will attempt to provide its own sealing force such as a rubber or asbestos gasket. Of course such gaskets cannot provide sufficient sealing force in many applications. Self-energized or low seating stress gaskets are generally used with connectors that produce no gasket crushing force or have some limitation or weakness in providing sufficient force to seat crush-type gaskets that are appropriate in high temperature service and many other application. Self-energized gaskets are also used when a connector is unable to provide substantial uniform seal integrity.
Prior clamp-type connectors have significant weakness in such areas. In a clamp-type connector, clamp segments deflect under load of fasteners. If such deflection is not accounted for, seal integrity is questionable because such prior clamp segments apply more clamping force near the fasteners and are therefore susceptible to leaks away from the fasteners. If this deflection is not accounted for, clamp segments and mating flange members are susceptible to contact interface damage in cyclic service. Therefore, a need exists in the industry for a safely articulated fastener incorporated into a remote operable clamp-type connector that effectively seals a joint even if a high seating stress, crush-type gasket is warranted or beneficial.
The mechanism disclosed in U.S. Pat. No. 4,483,458 (xe2x80x9cthe ""458 patentxe2x80x9d) cannot supply axial joint closing force because this device allows the clamp halves, the closing elements, and the pressure vessel housing to move axially relative to one another. Another result stemming from this relative movement is fatigue damage. The ""458 patent device will encounter unacceptable fatigue damage in cyclic operation, requiring frequent testing, repair, or replacement. The ""458 mechanism also requires external guide frames and anchor locations for automatic actuators and supports, such as foundations, that are not practical or economical. The ""458 mechanism also lacks positive locking fastening elements that retain the clamp halves. Under pressure, predictable radial and tangential forces will force these clamp halves apart. Also, this device must be reconstructed, depending on its orientation with respect to gravity.
U.S. Pat. Nos. 3,310,329 and 4,347,944 disclose flanges that comprise a unitary clamp band remote actuated to liberate and secure flange members. In both of these devices, unacceptably high stresses will be generated at the midpoint of the clamp band farthest away from the separation gap in the clamp band. These stresses will alternate between very high compression to very high tension as the clamp band is cycled from the open position to the closed position. All economical materials available for construction of the clamp band will undergo unacceptable fatigue damage, effectively limiting the useful life of these flanges. By analogy, the clamp band of these mechanisms can be compared to a single piece of wire bent back and forth until severe fatigue damage separates it into two pieces.
To avoid the problem of severe fatigue damage associated with aforementioned inventions, the prior art has incorporated further degrees of freedom in the clamp band with hinges that articulate segments of the connector to alleviate high bending stresses. U.S. Pat. Nos. 2,982,437 and 5,471,739 illustrate such hinged connectors. The hinge in these mechanisms is an example of a single point failure location. Furthermore, the actuator or drive that opens and closes the clamp band is another single point failure location. U.S. Pat. No. 3,144,165 discloses yet another example of a single point failure mechanism. Succinctly, these single point failure mechanisms are inherently unsafe.
In addition, ASME Boiler and Pressure Vessel Codes give rules for the minimum acceptable safe construction of pressure retaining components. The prior art discloses automated clamp connecting means that are unsafe and are not ASME Code compliant. Accordingly, there remains a need for an remote operable fastener mechanism, preferably comprising a clamp-type connector, suitable for normal and extreme service that is simply, reliable, rugged, and above all, safe.
There is a need in industry to be able to remote open and close a joint frequently with safely articulated fasteners that further incorporate a clamp-type connector that can provide a very large crushing force suitable to seat crush-type gaskets, such as a metal gasket. A further need exists to supply such a clamp-type connector that preferably accounts for segment deflection; thereby mitigating contact interface surface damage and providing uniform clamping force to crush such gaskets even in a location away from the clamp segment fasteners.
There is a need in the industry to be able to remote open and close a joint frequently with safely articulated fasteners; wherein, the fasteners open and close the joint without turning a threaded member to produce such remote open and close function because threads are easily damaged especially in xe2x80x9cdirtyxe2x80x9d operations. Moreover, operators using manually operated flanges benefit from a remote operable fastener mechanism adapted to quickly and simply retrofit such manual flanges to remote operation while accommodating at least part of the existing manual flange. Typically, an existing manually sealed flange pair will have been disposed on a vessel or pipe, such as a coke drum. A remote operable fastener mechanism, preferably comprising a clamp-type connector, that can utilize the manual flange already disposed on the units can generate significant process efficiency as well as improved safety for the unit.
All aspects of the embodiments of the invention draw attention to safety, simplicity, reliability, and ease of maintenance. The invention provides an important mechanism in providing a unique and safe system to remote operate the deposition of a pressure vessel. Remote operable is defined and used herein as the ability to operate without manual intervention from a location separated by distance. xe2x80x9cPluralityxe2x80x9d is defined to mean more than one similar or dissimilar items. The present invention comprises a substantially remote operable fastener, preferably incorporated into a clamp-type connector. This fastener comprises uniform sealing seal integrity to isolate internal volumes from the external environment, automatic primary remote operation, secondary manual operation, predictable operation using a small number of parts, and cost effective design. The embodiment is suitable for pressure retention and especially suitable for extreme pressure retention providing highly efficient access and enclosure in a batch-type operation of a low or extreme pressure vessel, and is especially suitable for high temperature or xe2x80x9cdirtyxe2x80x9d operations. In other words, it is especially suitable for extreme service.
The current invention provides a unique and safe fastener that can be operated at a distance removed from danger and can be used to retrofit or replace existing manually bolted flanges. The invention may be preferably incorporated into a remote operable joint connector that is advantageous for safely deheading a coke drum by disconnecting or connecting an inlet pipe to a coke drum, the drum-bottom closure to the coke drum, and the drum-top closure to the coke drum.
A standard multiple-bolted flange, as described in ASME B16.5, and the invention produce an axial joint closing force necessary to sustain joint sealing integrity. The invention is designed to supply the closing force with a magnitude large enough to produce a contact stress on a gasket that creates a sealing barrier between the internal and external environments of the joint.
In a preferred embodiment, the fastener is an element of a clamp-type connector comprising a clamp whose perimeter is divided into a plurality of clamp segments conjoined by the fastener. The fastener conjoins the clamp segments such that the failure of any single fastener element will not unconjoin the clamp segments or cause failure of the clamp-type connector; therefore, forces acting on them cannot rend the clamp-type connector""s articulation. The clamp perimeter of this embodiment can be cylindrical, but is not limited to a cylindrical profile. For example, joints may be rectangular or another known shape. Moreover, the joint can be opened and closed remotely or manually. A preferred embodiment incorporating the invention involves the inclusion of remote operable clamp segments, operable from a distant location.
The nature of the invention provides remote operation without compromising manual operation. Those skilled in the art will appreciate the self-contained nature of the fasteners, which allow the clamp-type connector to be manually opened and closed quickly, with only the use of a standard wrench. A significance of the invention""s clamp-type connector embodiment is its ease in transition and functioning from manual to remote operation.
The clamp-type connector embodiment of the invention comprises a remote operable actuator that provides a connecting force to a redundant plurality of these fasteners. In a preferred embodiment of the invention, these fasteners may comprise threaded bolts. There is a number of other joining devices that can be substituted for threaded bolt fasteners. Cams, hooks, cables, spring loaded locking tabs, linkages, gear driven members, rack and pinion members, chain linkages, and other known devices could be incorporated into each fastener to move the clamp segments into a closed, sealing position.
Energizing the fasteners causes the clamp""s perimeter to expand and contract in an opening and closing motion, liberating or retaining the flange members. When the perimeter of the clamp segments is increased, the female taper internal diameter of the clamp segments disengages the tapered male outer perimeter of the flange hubs. The male to female tapered interface between the flange hubs and the clamp segments allows the clamp segments to act as a restraint to effectively energize, lock, and secure the flange members together allowing a seal barrier to be created. Furthermore, the tapered flange hubs can create an axially compressing force that tends to drive the flange members into one another when the clamp is closed against the flange hubs. This closing occurs when the diameter of the clamp is contracted by the plurality of clamp segment fasteners. Therefore, gaskets requiring joint contact surface compression and/or seating force can be energized between the flange members creating a seal barrier to seal the vessel""s internal environment from its external environment. Stored energy in the clamp segment fastener secures seal integrity.
In the clamp-type connector embodiment of the invention, a conical make-up shoulder is a mechanical advantage wedge that multiplies fastener force generated by the fasteners into a resultant clamping force forcefully draws coupled flange members together, in turn, producing significant gasket compression force on a gasket squeezed between them.
In the clamp-type connector embodiment of the invention, one of the conical make-up shoulders is replaced by a substantially straight, non-angled make-up shoulder, such as that disposed on manually bolted flanges like those described by ASME B16.5. This arrangement allows an existing manually bolted flange to be retrofitted for remote operable operation by removing the manual bolts and disposing the invention about an existing flange. Typically, an existing manually sealed flange pair will have been disposed on a pair of structural units to be joined. Hazardous conditions of or about the joining of this flange pair, or the benefit of decreased joint connecting and/or disconnecting time gives birth to the need for remote operable devices, such as the invention. Because the invention can utilize a manual flange already in use, significant cost saving is realized. Several advantageous attachment mechanisms and methods are discussed herein. Such attachments disposed the clamp-type connector embodiment of the invention on new or existing structures each has its own advantages.
Moreover, the invention may be incorporated into a remote operable mechanism to assure uniform closing force along the entire clamp segment-to-flange member contact surface interface. This unique feature incorporates clamp segments adapted to make controlled contact at or about the midpoint of the clamp segment farthest away from the clamp segment fasteners (xe2x80x9cCC clamp segmentsxe2x80x9d). Further, guide members are adapted to act on the clamp segments to guide the contact of the clamp segments with respect to the flange members producing a controlled predictable contact. This controlled contact, together with CC clamp segments, uniformly preloads the entire joint by initiating contact between the clamp segments and the flange members substantially near or about the clamp segments midpoint farthest away from the clamp segment fasteners. The actuating device member, acting on the clamp segment fastener, provides a closing force, transmitted into the clamp segments resiliently deflecting them. This resilient deflecting occurs as the CC clamp segments are energized and forced to engage the flange members by the clamp segment fasteners. The closing force first provides connecting preload substantially at or near the CC clamp segments"" midpoints, then continuously provides the preload force closer and closer to the clamp segment fastener as the CC clamp segment is flexed about its midpoint. This unique feature causes the force on the clamp segment fastener to be uniformly distributed along each entire clamp segment-to-flange member contact surface interface. The uniform preload at the contact surface, in turn, supplies a uniform sealing force on the flange member-to-gasket member contact surface, creating a barrier between the joints"" internal and external environments.
Moreover, a unique way to assure the uniform preloading can be effectively incorporated with a remote operated joint opening and closing mechanism is shown in a preferred embodiment that utilizes guide pins attached to the clamp segments. These guide pins are restricted to travel in passageways fixed with respect to at least one flange member. The fixed motion of the guide pins, in turn, guides the radial motion of the clamp segments, relative to the flange members. This motion causes the clamp segments"" midpoints to return to the flange members at a predictably controlled location every time the clamp segments are remote actuated from the clamp segments"" open positions to the clamp segments"" closed positions.
When the clamp segments are secured to the flange members, friction between the flange members and the clamp segments tend to lock the clamp segments onto the flange members. CC clamp segments are resilient and when energized, are forcefully flexed into engagements with the flange members and energy is stored. This energy tends to return the clamp segments to their free state, away from the flange members; thereby, producing a relative unlocking force between the clamp segments away from the flange members that overcome the friction force holding them together. Those of ordinary skill in the art will appreciate the substantial benefit of this feature, which reliably overcomes the locking friction force between the clamp segments and the flange hubs, and the importance of this feature to the effective remote operable connecting and disconnecting of a joint.
In typical Delayed Coking applications well over a 1,000,000 pounds of force must be produced to obtain seal integrity at the drum-bottom flange. Even considering the number of connection and disconnection cycles over the typical life of a coke drum under such force, CC clamp segments dispel concerns of surface damage or wear at the clamp segment-to-flange member contact surface. Of course, surface damage or wear is directly related to the contact stress produced by the forces drawing the surfaces together. The contact stress in such an application is well below 4000 pounds per square inch. Furthermore, CC clamp segments"" initial contact positions are substantially the same as their final closed positions so very little sliding occurs between the clamp segments and the flange members, dispelling wear over the typical life of a coke drum. Compared to the prior art, in which wear may have been of concern, wear is not noticeably observed in the current invention.
In the closed position, the flange hubs have generally male conical profiles that mate with the clamp segments"" generally female conical profiles. The overlaying of the mating contact surfaces throughout a substantial part of the entire conical contact length insures proper contact with the mating flanged surfaces.
The clamp-type connector embodiment of the invention also allows for the creation of a self-contained mechanism. This embodiment does not require external devices, such as foundation reaction points or motion limiting devices, to function properly. The clamp segments can be further self-contained by incorporating the passageways for the pivot pins, and other clamp support passageways, into a self-containing support ring or a support plate that can dispose the clamp segments. These self-containing rings fix the orientation of the passageways, such that the clamp segments are guided from the open position to the closed position, relative to the flange members, and relative to each other, to assure proper connection and disconnection of the joint. Moreover, this self-contained clamp assembly can be removed as a single unit from the flange members quickly and easily for preventative maintenance. This approach is especially useful in a subsea environment where remote operable vehicles could retrieve this modular clamp assembly for easy transport to the surface, and replace the assembly with a new assembly, leaving flange members at their subsea location. Additionally, the fastener serves the dual purposes of containing and actuating the clamp segments, thus securely holding the gap between the clamp segments closed.
Advantageously, the fasteners may be of any construction. For safety reasons the clamp segment fastener elements should not comprises a failure path that could cause an opening of the gap upon failure of any one component. There are a number of clamp segment fasteners that would suffice to perform this function. Cams, hooks, cables, spring loaded locking tabs, linkages, gear driven members, rack and pinion members, chain linkages, swing bolts, and other known devices could fastener to unite the clamp segments.
Moreover, in the prior art, the transition between remote and manual operation is complicated. Some remote operated mechanisms must be disconnected before manual operation can occur. Moreover, the manual operation of these devices was both labor intensive and complicated by the remote operation. In contrast, the current fastener can be remote energized to either open and unlock the clamp gap or close and lock the clamp gap, both by remote actuable drive members or manually without disconnecting any components. This arrangement allows primary remote operation to be married with secondary manual operation.
The energy supplied to the clamp segment fastener by the remote actuable drive member is positively stored by the clamp segment fastener, thus securing the gaps between the clamp segments and locking the clamp-type connector onto the flange members even if the remote actuable drive member is disconnected. This feature allows the joint connection to remain safely and securely sealed, independent of the remote actuable drive member. Moreover, this arrangement allows energy stored in the clamp segment fastener to be increased or decreased manually even after it has been locked.
Additionally, any known actuable drive member, such as hydraulic or pneumatic cylinders or motors may energize the fasteners. Known mechanical advantage devices, such as gears, wedges, linkages, and cams could be incorporated with the actuable drive member. The fasteners can be adapted for interlock mechanisms to prevent inadvertent remote operation and such interlock mechanisms can be passive or active along with being force of pressure sensitive.
As was the case with the clamp-type connector embodiment, the fastener may interact with the clamp segment in a self-contained assembly. This assembly does not require external anchors or reaction structures to operate. Also, the clamp segment fastener will limit the opening motion of the clamp segments autonomously, and thus not require additional motion limiting devices.
The fastener is further adapted for remote tightening by utilizing a forgiving wedged locking device that can advance to easily adjust for varying magnitudes of standoff and applied force. The locking device interacts with a wedged clevis nut and is adjustably fixed to one of the structural units being fastened. A manual interlock holds the locking device in a locked position preventing remote operation when it is engaged against the locking device. As an alternate safety feature, a remote actuable drive member can be a spring-extend hydraulic cylinder such that when the remote actuable drive member is un-powered, spring force tends to force the locking device its locked position. The wedge angle will be preferably small so as to be self-locking due to friction contact. Those skilled in the art can easily derive wedge angle.
A resilient deflection is noticed in the clamp segments when fastener force is applied to them. If not accounted it can lead to non-uniform gasket compression force distribution along the clamp segment-to-flange member contact surfaces when deflection causes the clamp segments to produce more force on the mating flange members near the end of its segments. Of course, non-uniform gasket compression force distribution makes a joint susceptible to leaks.
Gaskets standoff initially holds the coupled flange members apart until the clamping force draws down the flanges, compressing and seating the gasket to producing a sealed joint. In a clamp-type connector embodiment of the invention, the clamp segments are adapted to make controlled contact at or about the midpoint of the clamp segment between the fasteners to provide uniform clamping force. CC clamp segments can be predisposed by forming or over-sizing to account for the aforementioned deflection. Fasteners deflect CC clamp segments into engagement with the flange members and tend to separate from flange members when un-energized by fasteners.
Compared to the mating of exact-sized clamp segments to flange members, CC clamp segments substantially reduce the distance the CC clamp segments must move under clamping force. Also, the initial contact area between the CC clamp segments and flange members is significantly greater than in the corresponding prior art mating components. Smaller open position gaps result in cost savings because the components of the fastener can be much shorter. Additionally, the open perimeter of the CC clamp segments is much smaller, saving space. Also frictional forces holding clamp segments onto the flange members are substantially overcome by the outwardly flexing action of the CC clamp segments away from the flange members when initially opened.
In a clamp-type connector embodiment of the invention, CC clamp segments are further adapted to maximize initial area contact between the flange members and the CC clamp segments. In this embodiment, CC clamp segments connecting to the flange members mitigate wear at the contact interface. When the CC clamp segments are moved on and off the flange members, the contact stress on the contact interface is significantly lowered because the contact area between the CC clamp segments and flange members is greatly increased.
The CC clamp segments, the fasteners, the remote actuable powered drive members, the locking devices, and the remote actuable powered locking devices actuators can all be functionally assembled in a self-contained portable assembly that can be disposed on flange members. Several attachment details are appropriate to dispose such assembly to the flange member or a vessel. The assembly can be mounted to the vessel or to a structural unit such as a flange member.
In Delayed Cokers it is advantageous to quickly adapt a manual bolted flange to a remote operable connector on the existing coke drum flange without the use of a bolted spool adapter for bolting the remote operable connector to the existing flange. In doing so more than one seal must be achieved. The clamp-type connector embodiment of the invention can be disposed on the existing flange without welding to the coke drum and only one seal must be achieved. This presents very significant cost savings to coke drum owners who would potentially shutdown their operation to install a new coke drum flange. Advantageously, the invention can be installed between Delayed Coking cycles.
A cleaning mechanism and cleaning method useful in the clamp-type connector embodiment provide for a cleaning substance, like steam, to cleanse all contact interfaces including the gasket interface with the flange members. It comprises a perforated conduit adapted between the inside of the clamp segments and the outside of the flange members. It can be segmented similarly to the clamp segments. This cleaning mechanism is especially useful in xe2x80x9cdirtyxe2x80x9d operations such as Delayed Coking. The clamp-type connector embodiment of the invention can be used to automate a Delayed Coking process to increase efficiency and safety. It can remote connect or disconnect a feed line, a drum-bottom head, a drum-top head, a decoke chute or a drill stem centralizer to the coke drum.
In a preferred embodiment, the remote operable fastener comprises a plurality of threaded bolts. If one bolt fails, the additional bolts provide the safe articulation needed for safety.
Advantageously, the design of the invention and its incorporation into a clamp-type connector allows for dry assembly of the component parts. No grease or other lubricants are required during assembly. Furthermore, depending upon the material from which the components are manufactured, this fastener can be utilized in environments up to 1800xc2x0 F.